The invention relates to a laser diode module comprising:
a rectangular box-like metal casing with a bottom, two long and two short sidewalls, a tubular passage for a glass fibre being provided in one of the short sidewalls, and no less than eight guide pins being passed through the bottom in a standardized DIL-order, no less than one of the guide pins being inserted in the bottom by means of electrically conducting material and the remaining guide pins being inserted in the bottom by means of feedthrough insulators; PA0 a thermoelectric cooler having two thermal contact pads, one contact pad being thermoconductively coupled to the bottom of the metal casing; PA0 a plate-formed metal base carrier which is thermoconductively connected to the other thermal contact pad of the thermoelectric cooler, this base carrier accommodating: PA0 connecting lines for electrically connecting the laser diode, the photodiode, the thermistor, the thermoelectric cooler and the metal base carrier to the respective guide pins.
a first sub-carrier with a laser diode attached, PA1 a second sub-carrier with a photodiode attached, PA1 a support for arranging the glass fibre such that its end is facing the front facet of the laser diode, and PA1 a thermistor thermally coupled with the base carrier; and
In optical communication systems laser diode modules are used for electro-optical conversion of the electrical data signals to be transferred, whilst there is already widespread use of systems with data bit rates of 140, 280 and 565 Mbit/s. In the 565 Mbit/s systems a laser diode module with the configuration described in the preamble has become a de facto standard. In addition to the laser diode and the end of the glass fibre coupled thereto this standard module comprises a thermoelectric cooler, a thermistor and a photodiode facing the rear facet of the laser diode, which are used for monitoring and stabilizing the temperature and the delivered optical power of the laser diode.
In the field of optical communication there is a trend towards strongly increasing bit rates in the short term, according to which trend systems having a bit rate of 2.4 Gbit/s are already being developed. At these increasing bit rates it turns out that from approximately 1 Gbit/s onwards not so much the laser diode itself, but rather the laser diode module as a whole forms a constraining factor, so that not only the thermal and mechanical characteristics of the module should be given consideration to but also its electrical characteristics for higher frequencies. Specifically the rather large dimensions of the technically available thermoelectric coolers and the relatively large length of several connecting wires to the guide pins play an important role in this matter. A possible solution is redesigning the laser diode module as a whole for bit rates exceeding 1 Gbit/s and modifying in this new design the dimensioning of the casing and the order in which the guide pins are fed through the casing so that the electrical characteristics for higher frequencies are more favourable than with the standard module. The solution is not only costly, but also accompanied with the disadvantage that the printed circuit board accommodating the electric circuit elements to be connected to the laser diode module has to be redesigned, since the connecting points for the guide pins of the module can in that case no longer be selected according to a standardized DIL order.